Drawn to the Dead or Just Decoration? Cyphomyrmex costatus Collect Arthropod Body Parts
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Date
2023-12
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The Ohio State University
Abstract
Cyphomyrmex costatus Mann 1922 is a small fungus-growing ant, distributed in warm temperate regions in southern Mexico to northern South America. Like all fungus-growing ants, C. costatus colonies have a mutualistic relationship with their garden in which they collect material to nourish it while simultaneously feeding on it. Along with insect droppings and scraps of vegetation fed to the garden, worker ants collect the remains of various arthropods. Weber (1957) reported the use of empty arthropod carcasses in C. costatus gardens as garden substrate, yet no one has analyzed the species richness and evenness (e.g., faunal profile) of these arthropods, nor tested predictions regarding their potential function. Cyphomyrmex costatus line their nest chambers with dozens of exoskeletons that range from arachnids to other ant species. This study explores possible explanations for this unusual foraging behavior of C. costatus, collected in Soberanía National Park, Panama. One hypothesis is that these "arthropod remains" act as another kind of substrate for the fungus to consume (Weber, 1957), but observations in our laboratory and the field have cast doubt. Instead, we predict that the remains serve as either chemical or visual signals to dissuade other arthropods from entering the nest. This study aims to determine if C. costatus workers, (1) preferentially select ant heads with intact chemical profiles versus controls (solvent-washed heads), (2) preferentially select ant heads that originated from another ant nest, and (3) preferentially gather insect remains of particular species in nature. Our behavioral choice assay results indicated that chemical profile presence as well as ant head origin did not dissuade the C. costatus ants from collecting ant head presented to them. When analyzing the taxonomic diversity of the collected body parts for 13 colonies, we could identify 82.6% of the 884 body parts to the order, family, subfamily or genus taxonomic level. Among the identified material, 77% were species of ants. We also discuss the availability and abundance of the collected ant species in the environment. Our investigation provides new insights regarding C. costatus ecology and interspecific interactions
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Keywords
Entomology, Natural History, Ecology, Myrmecology, Cyphomyrmex costatus, Behavior